Workaround bugs in Proxy serialization

[Andrew Haley]

Andrew Haley writes:
 > Looking at the Classpath sources for ObjectInputStream, it seems that
 > the area where I had so much trouble has been reworked.  I'll
 > investigate importing those classes into libgcj.

I've thought about this some more, and come to the conclusion that the
best thing is to check this workaround into libgcj as gcj local and
re-test the next time a Classpath merge is done.

Andrew.